The present invention relates generally to material handling equipment and relates more particularly to pop-up units for use in material handling equipment.
The manufacture and/or packaging of many types of commercial articles often involves the use of material handling equipment. One example of material handling equipment is a bench or workstation at which certain assembly or packaging steps for an article are performed. Another example of material handling equipment is a conveyor system for transporting an article from one workstation to another.
As can readily be appreciated, an article that is seated on top of a bench or workstation often must be repositioned or rotated thereon so that certain assembly or packaging steps can be performed. Similarly, it is often the case that the direction in which an article is traveling along a conveyor system must be altered or its movement altogether stopped. For these reasons, various types of repositioning devices and stopping devices have been devised that are adapted for use in material handling equipment.
One type of device that is adapted for use in material handling equipment is a pop-up unit, which is typically pneumatically-controlled. The pop-up unit is typically either in the form of a pop-up ball, which is designed to permit omnidirectional movement of an article thereon, or a pop-up stop, which is designed to impede or to prevent movement of an article thereon. Examples of various pneumatic pop-up units are disclosed in U.S. Pat. No. 6,516,934, inventor Masciarelli, which issued Feb. 11, 2003, and which is incorporated herein by reference. In one embodiment, the pneumatic pop-up unit comprises a stamped metal housing. The stamped metal housing is a generally cylindrical structure having an open top, a circular side wall, and a circumferential flange extending radially outwardly from the open top. A nipple is mounted in a bottom wall of the housing, the nipple being adapted for attachment to a pressurized gas supply. The pneumatic pop-up unit also comprises a stamped metal cap. The stamped metal cap includes an annular top wall, an inner side wall, and an outer side wall, the outer side wall being bent down across the outside edge of the flange and then radially inwardly against the bottom surface of the flange. The pneumatic pop-up unit additionally comprises a two-piece stamped metal piston slidably mounted within the housing and a stamped metal race disposed within the piston. The pneumatic pop-up unit further comprises a monolayer of ball bearings arranged within the race and a primary ball seated directly on top of the ball bearings, the primary ball being free to rotate in any direction. The primary ball is appropriately dimensioned so that its top extends through an open top of the piston. The pneumatic pop-up unit further comprises a rubber seal fitted around the piston and a coiled spring for biasing the piston downwardly within the housing. Typically, when the pneumatic pop-up unit is at rest, the coiled spring biases the piston downwardly within the housing such that the primary ball does not extend upwardly at all through the top of the cap. By contrast, when the pneumatic pop-up unit is actuated, pressurized gas is admitted into the housing through the nipple, causing the piston to move upwardly until the top of the primary ball extends through the top of the cap. In this manner, an article positioned on top of the unit is raised by and becomes seated on top of the primary ball.
Although the above-described pop-up unit has been found to be generally satisfactory for its intended purpose, the present inventor has noted some shortcomings in connection therewith. For example, once the internal components of the pop-up unit have been placed in the housing and the cap has been secured to the housing, the internal components of the pop-up unit, such as the primary ball, cannot be removed from the housing without removing the cap from the housing. However, removal of the cap from the housing is often cumbersome and/or may cause damage to the cap and/or the housing. This is unfortunate because the primary ball or other internal components of the unit can become worn and/or dirty over time. Consequently, the option most often employed is to replace the entire unit, as opposed to, for example, replacing a worn primary ball.
Another shortcoming noted by the present inventor is that the primary ball, because of its spherical shape, has very little surface area that actually comes into contact with the article being handled. As a result, because of the limited contact area between the primary ball and an article positioned thereon, it can be difficult at times to steer the article in a desired direction using the primary ball.
Still another shortcoming noted by the present inventor is that, over time, the rubber seal positioned around the piston tends to become worn. Such wear may be caused, for example, by the repeated sliding of the seal against the inner side wall of the housing as the piston is raised and lowered. As can be appreciated, the wearing of the seal may negatively impact the performance of the pop-up unit since leaks in or around the seal allow pressurized gas to escape from the housing, thereby making it more difficult to raise the piston when desired.
Besides pop-up units, another type of device that is adapted for use in material handling equipment is a unidirectional rotating support assembly, which is typically in the form of a roller or wheel. For example, in U.S. Pat. No. 6,401,900 B1, inventor Masciarelli, Jr. which issued Jun. 11, 2002, and which is incorporated herein by reference, there are disclosed various unidirectional rotating support assemblies adapted to be located in apertures provided in material handling equipment, such as the surface of a workstation, a scissors lift, a cart conveyor or the like. According to this patent, a unidirectional rotating support assembly typically includes a unidirectional rotating member, a support member and a rotating member support mechanism that rotatably supports the unidirectional rotating member with respect to the support member. The support member is configured or arranged so a portion thereof is received in the aperture in such a fashion that the support member has limited, if any, ability to move with respect to the work station surface. Thus, the rotating member also is maintained in a relatively fixed position with respect to the work surface. The support member includes an aperture therein, whose long axis is generally perpendicular to the work surface. The rotating member support mechanism is arranged so a portion thereof extends across this aperture or opening in the support member such that the unidirectional rotating member is disposed therein. The supporting mechanism in a particular embodiment is an axle and the unidirectional rotating member can be one of a wheel or a roller.
As noted above, the wheel or roller of the aforementioned unidirectional rotating support assembly is typically maintained in a fixed position above its respective work surface. Consequently, as compared to a pop-up unit, whose ball or stop may be raised and lowered as desired, the wheel or roller of the above-described unidirectional rotating support assembly is fixed in a raised position and cannot be lowered when repositioning or steering of an article is not desired. The present inventor has found this to be disadvantageous as the raised wheel or roller limits the amount of usable surface area of the work surface.
Other documents of interest may include the following, all of which are incorporated herein by reference: U.S. Pat. No. 6,457,865 B1, inventor Masciarelli, Jr., issued Oct. 1, 2002; U.S. Pat. No. 6,164,429, inventor Masciarelli, Jr., issued Dec. 26, 2000; U.S. Pat. No. 6,120,185, inventor Masciarelli, Jr., issued Sep. 19, 2000; U.S. Pat. No. 6,019,211, inventor Masciarelli, Jr., issued Feb. 1, 2000; U.S. Pat. No. 4,732,490, inventor Masciarelli, issued Mar. 22, 1988; U.S. Pat. No. 4,706,793, inventor Masciarelli, issued Nov. 17, 1987; U.S. Pat. No. 4,660,994, inventor Masciarelli, issued Apr. 28, 1987; and U.S. Pat. No. 4,627,526, inventor Masciarelli, issued Dec. 9, 1986.